ERP figures for Australia and its states and territories are calculated using a base figure obtained from the most recent Census of Population and Housing. The Census is the principal source of information about Australia's population and has been held every five years since 1961. The most recent Census was conducted in August 2006. To obtain ERP figures from the Census results, the raw Census population count is adjusted for visitors from overseas and interstate on Census night, Australian residents temporarily overseas on Census night and an estimate of both the number of people missed and those counted more than once. ERP figures for dates between Censuses are estimated by adding births and net overseas migration to the Census-based figure, and subtracting deaths. For state and territory figures, interstate migration estimates are also applied.

Over the past decade, Australia's ERP has grown by just under 2.4 million people (or 13.1%). The growth of Australia's population has two components: natural increase (the excess of births over deaths) and net overseas migration (the sum of permanent and long-term migration). For state and territory estimates, a third component - net interstate migration - is also included. Since Federation in 1901, Australia's population has increased by just under 17 million people (graph 7.2).

7.2 Population

Population growth has occurred unevenly across the states and territories (table 7.3). Consequently, the proportion of Australia's population resident in each state and territory has changed over time. From 1956 to 2006, the proportion of the Australian population living in New South Wales decreased, from 37.7% to 32.9%, as did Victoria (from 27.5% to 24.8%), South Australia (9.0% to 7.6%) and Tasmania (3.4% to 2.4%). The proportion of Australia's population living in all other states and territories increased over the period, with Queensland increasing from 14.7% to 19.8%, Western Australia from 7.2% to 9.9%, the Australian Capital Territory from 0.4% to 1.6% and the Northern Territory from 0.2% to 1.0%. Western Australia overtook South Australia to become the fourth most populous state in 1982.

Over the last 50 years, the population more than doubled from 9.4 million in 1956 to 20.7 million in 2006. Natural increase has been the main component of population growth in Australia over this period, contributing around 60% of the total increase. Net overseas migration, while a significant source of growth, is more volatile, fluctuating under the influence of government policy as well as political, economic and social conditions in Australia and the rest of the world.

Yearly growth due to natural increase and net overseas migration from 1956 to 2006 is shown in graph 7.4.

Fifty years ago, Australia was experiencing a baby boom. In 1956, the excess of births over deaths, or natural increase, was 126,000 persons. Natural increase peaked at 151,000 in 1961, after which, declining fertility led to a fall in natural increase. Natural increase rose again in the late-1960s, reaching a peak of 165,700 in 1971. A decade later it had fallen to 126,800. In 1996, natural increase fell below 125,000 for the first time since Federation. This downward trend continued, reaching the second lowest natural increase over the 1956-2006 period (115,200 persons) in 2003. In recent years there has been a slight rise in natural increase to 131,200 persons in 2006. Nonetheless, ABS population projections suggest that continued sub-replacement fertility, combined with an increase in deaths due to an ageing population, will result in natural increase falling below zero around the middle of this century.

In 2006 the crude death rate was 6.4 deaths per 1,000 population, falling from 9.1 in 1956. The crude birth rate declined from 22.5 births per 1,000 population in 1956 to 12.8 in 2006. The lowest crude birth rate during this period, 12.4 births per 1,000 population, was recorded in 2004. Crude birth and death rates from 1956 to 2006 are shown in graph 7.5.

Over the last 50 years the absolute number of people increased in all age groups. However, the proportion of the population in older age groups increased while the proportion in younger age groups declined. Graph 7.6 shows the proportions of the population by age group and sex in 1956 and 2006, illustrating the ageing of Australia's population. Australia's population is ageing because of sustained low fertility, resulting in proportionally fewer children in the population, and increased life expectancy, resulting in proportionally more older people in the population.

7.6 Age distribution of population

In 1956 there were 126,500 more males than females in Australia's population, while in 2006 there were 120,800 more females than males. Since 1979 Australia has been home to more females than males. At June 2006, the sex ratio of Australia's population was 98.8 males per 100 females.

As shown in graph 7.7, people aged 0-14 years represented 29.4% of Australia's population in 1956, while those aged 15-64 years represented 62.2%, those aged 65 years and over represented 8.4% and those aged 85 years and over represented 0.4%. Although Australia's population continued to grow since 1956, the proportion of children aged 0-14 years decreased to 19.6% by 2006. In contrast, the proportion of people aged 15-64 years increased to 67.5% by 2006 and the proportion of the population aged 65 years or more increased to 13.0%. The proportion of those aged 85 years and over increased fourfold to 1.6%.

The change in the age structure of Australia's population over time is illustrated by the change in the median age (the age at which half the population is older and half is younger). In 2006 the median age of the Australian population was 36.6 years, an increase of 5.5 years over the median age of 31.1 years in 1986. Graph 7.8 shows the median ages of the population of the states and territories in 1986 and 2006.

In 2006 the population of Tasmania had the highest median age of all states and territories (38.8 years), closely followed by South Australia (38.7 years). The Northern Territory (30.9 years) had the lowest median age in 2006.

Tasmania experienced the largest increase in median age over the 20 years to 2006, increasing by 8.3 years from 30.5 years in 1986 to 38.8 years in 2006. The next largest increase was South Australia, increasing by 6.7 years, from 32.0 years in 1986 to 38.7 years in 2006.

In 2006 there were just under 2.7 million older Australians, that is people aged 65 years or more in Australia, an increase of 54,700 people (2.1%) over 2005. All states and territories experienced growth in this age group, with the Northern Territory and the Australian Capital Territory experiencing the greatest increases (7.0% and 3.3% respectively) (table 7.9).

The number of people aged 85 years and over in Australia has increased by 6.4% from 2005 to 2006, now equalling just under 322,000. Again, growth in this age group occurred in all states and territories, with the Australian Capital Territory experiencing the greatest increase of 8.3%.

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